In the manufacture of halosilanes, and notably trihalosilane, through the hydrohalogenation of metallurgical grade silicon or through hydrogenation of tetrahalosilane in the presence of hydrogen and metallurgical grade silicon, a resulting process stream can include a slurry. The slurry typically comprises the desired halosilanes accompanied by unreacted silicon particles and other polyhalosilane/polyhalooxysilane products (e.g., Si2X6, Si2OX6, where X=F, Cl, Br, or I), and metal halides (e.g., AlX3). It is desirable to recover the liquids from the slurry, thereby producing a solid, high-chloride residue. The solid residue can be further processed to reclaim the chloride value with minimal loss of higher value hydrochlorosilanes (see, e.g., U.S. 2006/0183958A).
A batch dryer is effective to remove halosilanes from the slurry, but it has disadvantages. For example, it may take in excess of 10 hours due to inadequate heating capacity and/or the presence of heavies (e.g., polyhalosilanes, polyhalooxysilanes, metal halides), which have high boiling points relative to tetrahalosilane (SiX4). In some cases, the boiling point is 100° C. higher than the boiling point of SiX4. Additionally, abrasive solids in the slurry cause erosion on the dryer walls. The batch dryer typically requires replacement several times during the lifetime of a halosilane unit, such as every 4-5 years, due to extensive wear and tear. Thus, a need exists for a better process to separate the slurry liquids and solids.